WASHINGTON
— A few minutes into the oral argument over the juvenile death penalty last week at the US Supreme Court, Justice Anthony Kennedy posed a question. He wondered whether significant international opposition to juvenile executions should influence how an American justice interprets the Constitution's prohibition against cruel and unusual punishment.

"Does that have a bearing on what is unusual?" Justice Kennedy asked.

The query was aimed at a government lawyer, but it could have just as well been directed to the court itself.

How the court approaches Kennedy's question is important for two reasons. First, it highlights an emerging trend on the nation's highest court in which a majority of justices are increasingly willing to cite international law and foreign judgments to support their decisions. Second, with substantial opposition to capital punishment in Europe and elsewhere, it could play a key role in determining the outcome of the juvenile death-penalty case.

"I think the way Justice Kennedy asked his question was telling," says Richard Wilson, a law professor at American University in Washington who attended the court session. "He asked about whether the word 'unusual' in the Eighth Amendment phrase 'cruel and unusual' ... refers to 'unusual' in the United States, or is it 'unusual' in the world?"

Where the justices stand

Currently, six of the justices - including Justices Kennedy and Sandra Day O'Connor - support using references to international law in decisions. Three justices have announced opposition to the trend.

Critics view this growing internationalist approach as a potential source of unrestrained judicial activism. They say it is being driven by justices willing to use international law as cover to impose their own policy preferences rather than remaining faithful to the original intent of the Constitution's framers.

Supporters of the trend see it as a progressive safeguard to fundamental freedoms, with justices seeking to broaden their horizons beyond the parochial interests of a single country in recognition of international legal norms that reflect the shared values of mankind.

"What the court is saying is we can look to the world community for guidance and not to put blinders on to what is happening in the rest of the world," says Professor Wilson, who wrote a friend-of-the-court brief on behalf of 48 countries urging the justices to declare the juvenile death penalty unconstitutional.

The court is sharply divided on that question. Four justices had earlier announced their willingness to strike down the juvenile death penalty. Three others seem just as determined to uphold it. That leaves Justices O'Connor and Kennedy in the middle, with one of them potentially wielding the deciding fifth vote.

Given that both justices are apparently open to looking overseas for support in key cases, the international aspect of the case could prove decisive.

In the past four years, only five countries have executed individuals for crimes they committed when younger than 18 - the Democratic Republic of Congo, China, Iran, Pakistan, and the United States, according to a friend-of-the-court brief. It adds that all but two countries - Somalia and the US - have ratified the UN's Convention on the Rights of the Child, which bars capital punishment for juveniles.

To supporters of the juvenile death penalty and other legal analysts, such evidence of international rejection of juvenile executions should be irrelevant to US constitutional analysis. "Why should we care what foreign countries think our Constitution means?" asks John Yoo, a professor at Boalt Hall School of Law at the University of California in Berkeley.

"We could certainly ask them what they think their constitution means, but they are not part of our political community. And that is what the Constitution does - it recognizes a political community and establishes its rules for self-government," Professor Yoo says.

Tom Geraghty has a different view. "All countries with our tradition of jurisprudence have decided that the application of the death penalty to juveniles is violative of human rights norms," says Mr. Geraghty of the Bluhm Legal Clinic at Northwestern University School of Law in Chicago.

He wrote a friend-of-the-court brief on behalf of 13 individuals and four organizations awarded the Nobel Peace Prize. The brief urges an end to the juvenile death penalty. "The Nobel Peace Prize and its winners are a testament to the relevance of global opinion and practice in the area of human rights, and the importance of respecting internationally accepted standards of morality," Geraghty's brief says.

Supreme Court repartee

Supreme Court justices have long cited international decisions. But several cases in recent years have not only raised red flags among critics but also prompted dissents from within the court itself.

In 2002, when the court struck down the death penalty for mentally retarded individuals, Justice John Paul Stevens noted in his majority opinion that the practice was "overwhelmingly disapproved" within the world community. That drew a response from Chief Justice William Rehnquist: "I fail to see ... how the views of other countries regarding the punishment of their citizens provide any support for the court's ultimate determination."

In October 2002, Justice Stephen Breyer cited decisions of three foreign courts - the British Privy Council, the European Court of Human Rights, and the Supreme Court of Canada - supporting legal principles he felt should be applied in the case of a US death-row inmate: "Just as attention to the judgment of other nations can help Congress determine the justice and propriety of America's measures, so it can help guide this court when it decides whether a particular punishment violates the Eighth Amendment."

Justice Clarence Thomas, in a written reply, responded: "While Congress, as a legislature, may wish to consider the actions of other nations on any issue it likes, this court's Eighth Amendment jurisprudence should not impose foreign moods, fads, or fashions on Americans."

In June 2003, Kennedy cited a decision by the European Court of Human Rights for support in his landmark decision upholding gay rights in a Texas case: "The right the petitioners seek in this case has been accepted as an integral part of human freedom in many other countries."

In a dissent, Justice Antonin Scalia replied: "Constitutional entitlements do not spring into existence ... as the court seems to believe, because foreign nations decriminalize [homosexual] conduct."